1. Field of the Invention:
The present invention relates to a muffler for an internal combustion engine, and more particularly to a muffler for use as part of an internal combustion engine.
2. Description of the Prior Art:
Internal combustion engines are generally coupled with silencers or mufflers for expanding and compressing an exhaust gas emitted from the engine to dissipate the energy of the exhaust gas for attenuating the sound produced thereby. The muffler normally comprises an outer box of sheet steel defining therein an expansion chamber. However, the outer box of sheet steel cannot provide sufficient heat and sound insulation, and is relatively heavy. There has been proposed a muffler composed of an outer box of sheet steel and a layer of glass wool applied to the inner wall surface of the outer box. Although the proposed muffler can attain a certain degree of heat and sound insulation, it is complex in construction and also has an increasd weight.
The outer box of a muffler may be constructed of a sound insulation material formed by baking inorganic or organic fibers. Since muffler outer boxes are generally in the form of an elongate tube with front and rear ends closed, it may be advantageous in the manufacturing process to form a plurality of separate bodies of a sound insulation material and then join the formed separate bodies with an adhesive, thereby constructing a muffler outer box.
The muffler outer box is strongly subjected to the influence of heat and pressure variations when in use, and hence is required to have a mechanical strength great enough to withstand these stresses. Where the outer box is composed of the joined separate bodies of formed sound insulation material, the joined portions of the outer box are mechanically weaker than the rest of the outer box.
The present invention has been made in an effort to solve the above conventional problem.